The present invention relates to a surgical drill of the type commonly used for performing otological surgery in the middle ear, and to a novel bur or bit adapted for use with such a drill.
In performing otological surgery, it is common to employ a drill which comprises a small handpiece which houses an electric motor and a chuck, with the chuck being rotated by the motor under the control of a foot operated switch. The forward end of the housing mounts a tubular metal support sleeve, and a metal drill bur is adapted to be inserted into the sleeve so that the inner end of the bur rotatably and releaseably engages the chuck. To provide for the concentric rotation of the bur within the support sleeve, the shank of the bur incorporates an integral cylindrical metal bearing surface which has a diameter greater than the remaining portion of the shank, but which is somewhat less than the internal diameter of the bore of the support sleeve. The tolerance or spacing between the bearing surface of the shank and the internal bore of the support sleeve is relatively loose, in order to avoid the development of excessive heat from the metal to metal contact between the bearing and the support sleeve during the high speed rotation of the bur. This required spacing between the bearing surface and the bore of the support sleeve is disadvantageous however, since it renders precise control of the surgical operation difficult, and since it permits debris resulting from the drilling operation to move between the bearing surface and bore of the sleeve and into the interior of the sleeve. This in turn can result in contamination, which is difficult to remove, and it can also result in the scoring of the bearing surface of the bur.
It is also common for the burs of such surgical drills to be provided with cutting tips of a variety of configurations and sizes, so that a properly designed cutting tip may be selected in accordance with the particular procedure to be performed. However, since the cutting tips are very small, it is difficult for a surgeon to identify a desired bur, particularly when the bur is mounted in the handpiece.
It is accordingly an object of the present invention to provide a surgical drill and bur for use therewith, and which effectively overcomes the above noted disadvantages and limitations of the prior art devices.
It is a more particular object of the present invention to provide a surgical drill and bur of the described type, and wherein the tolerance between the bearing surface of the bur and the bore of the support sleeve is sufficiently close so as to provide a seal therebetween which prevents the passage of debris past the bearing surface and into the support sleeve, and while maintaining the generation of frictional heat within acceptable limits.
It is also an object of the present invention to provide a surgical drill and bur of the described type, and wherein the bur includes provision for the ready identification of the configuration of size of the cutting tip.